Velocity Structure of the Izu–Ogasawara Island Arc

A study of the Izu–Ogasawara Island Arc reveals that its crustal velocity structure mirrors continental crust characteristics, with distinct upper (4.5–6.0 km/s), middle (6.0–6.5 km/s), and lower (6.5–7.5 km/s) layers, including a two-part lower crust. The research, conducted using unified seismic surveys from 2004, found that the arc's development involves crustal thickening followed by rifting and back-arc opening, leading to thinning. Notably, the Shikoku Basin exhibits a thin crust (≈10 km) with high-velocity lower layers (>7 km/s), while the Ogasawara Ridge shows a complex structure with localized thin crusts. These findings provide insights into the arc's geological evolution and contrast with the Parece Vela basin.

TAKAHASHI, N., KODAIRA, S., SATO, T., YAMASHITA, M., KAIHO, Y., MIURA, S., NO, T., TAKIZAWA, K., NOGUCHI, N., SHIMOMURA, N., & KANEDA, Y. (2015). Velocity Structure of the Izu–Ogasawara Island Arc. Journal of Geography (Chigaku Zasshi), 124(5), 813–827. https://doi.org/10.5026/jgeography.124.813